Vehicle fuel systems comprise, among other items, a fuel tank fitted with a filler neck, a variety of fuel valves, a tubing for supplying fuel to the ignition system and a fuel vapor treating system (e.g. an active carbon filter recovery system), collectively referred to herein after in the specification and claims as a canister, to which fuel vapor from the fuel tank flows and is then used for enriching the fuel mixture fed to the ignition system.
Fuel fluid (in the form of liquid, droplets, spray and vapor) from the fuel tank flows via the one or more valves, which are connected via suitable tubing, to a liquid trap intermediate the fuel vapor recovery system and the tank.
The liquid fuel tank (LFT) receives fuel fluid flowing from the fuel tank which flows at a relatively high velocity owing to pressure and temperature changes, and thus vapor flowing from the fuel tank carries along with it also a considerable amount of liquid fuel in the form of droplets (as a result of a venturi effect). The liquid trap entraps the liquid fuel and admits fuel vapor flow towards the vapor recovery system. The liquid fuel then returns back to the fuel tank, upon pressure decrease within the fuel tank.
A liquid fuel trap is important in those cases where the various valves fitted within the tank are internally installed, i.e. do not project from an upper wall of the tank, where siphons may be generated at tubes connecting the valves to the liquid trap. Such siphons interfere with venting the tank on the one hand and, on the other hand, interfere with draining of the devices.
Still another problem occurring with liquid fuel traps is that the pressure within the fuel tank decreases toward the canister owing to head loss over the different valving and tubing and where the canister outlet is at atmospheric pressure. Accordingly, in some instances, when the pressure within the LFT drops below the pressure within the fuel tank, the fuel trap may in fact drag liquid droplets from the fuel tank towards the canister owing to motion of the fuel within the fuel tank of a vehicle resulting in temperature increase, pressure increase and generation of vapor or droplets which may enter the liquid trap and flow toward the canister. Furthermore, the pressure difference between the LFT and the fuel tank requires suitable arrangements for progressively discharging liquid fuel back into the fuel tank, i.e. not relying on gravity forces but rather actively propelling the liquid fuel.
It is an object of the present invention to provide a liquid fuel trap (LFT) for a vehicle's fuel system, in which the expansion tank is made of a plastic material and is adapted for fitting within the fuel tank.
It is a primary object of the invention to provide such a liquid fuel trap wherein liquid is prevented from flowing into the expansion tank thereof to thereby prevent liquid flow toward the canister.
It is further an object of the disclosed invention to provide a liquid fuel trap (LFT) of the aforementioned type in which means are provided for actively propelling fuel vapor into the fuel trap, and optionally for actively discharging liquid fuel into the fuel tank, responsive to fuel motion within the fuel tank.